CHICAGO – Even the best artists hem and haw over their work, including Rembrandt. An intense X-ray beam has revealed that the artist painted the same face in four locations on one canvas before settling on one spot and covering up the rest.

The oil painting, Rembrandt’s 1662 “Syndics of the Drapers' Guild,” depicts five drapers — cloth experts — working while a servant behind them looks out at the viewer.

Chemist Joris Dik of the Delft University of Technology in the Netherlands examined the pi...